Receptor-mediated endocytosis of the intrinsic factor—cobalamin complex in HT 29, a human colon carcinoma cell line

AbstractA HT 29 cell line derived from human colonic carcinoma was shown to express the intrinsic factor receptor, with about 5000 binding sites per cell and an association constant of 20 × 109 1/mol at pH 7.4 and 4°C. The number of binding sites increased dramatically between 7 and 10 days of culture time. Endocytosis of the intrinsic factor-cobalamin-receptor complex was inhibited by two ways: at 4°C and at 37°C by incubating the cells with vinblastine, monensin and chloroquine. The plasma membrane receptor was cross-linked to [57Co]cobalamin-intrinsic factor and solubilized with Triton X-100. The cross-linked complex had a relative molecular mass of 330 kDa in native PAGE

Uptake and transport of B12-conjugated nanoparticles in airway epithelium

Non-invasive delivery of biotherapeutics, as an attractive alternative to injections, could potentially be achieved through the mucosal surfaces, utilizing nanoscale therapeutic carriers. However, nanoparticles do not readily cross the mucosal barriers,with the epitheliumpresenting a major barrier to their translocation. The transcytotic pathway of vitamin B12 has previously been shown to ‘ferry’ B12-decorated nanoparticles across intestinal epithelial (Caco-2) cells. However, such studies have not been reported for the airway epithelium. Furthermore, the presence in the airways of the cell machinery responsible for transepithelial trafficking of B12 is not widely reported. Using a combination of molecular biology and immunostaining techniques, our work demonstrates that the bronchial cell line, Calu-3, expresses the B12-intrinsic factor receptor, the transcobalamin II receptor and the transcobalamin II carrier protein. Importantly, the work showed that sub-200 nm model nanoparticles chemically conjugated to B12 were internalised and transported across the Calu-3 cell layers,with B12 conjugation not only enhancing cell uptake and transepithelial transport, but also influencing intracellular trafficking. Our work therefore demonstrates that the B12 endocytotic apparatus is not only present in this airway model, but also transports ligand-conjugated nanoparticles across polarised epithelial cells, indicating potential for B12-mediated delivery of nanoscale carriers of biotherapeutics across the airways

Quantitative modeling of the physiology of ascites in portal hypertension

Although the factors involved in cirrhotic ascites have been studied for a century, a number of observations are not understood, including the action of diuretics in the treatment of ascites and the ability of the plasma-ascitic albumin gradient to diagnose portal hypertension. This communication presents an explanation of ascites based solely on pathophysiological alterations within the peritoneal cavity. A quantitative model is described based on experimental vascular and intraperitoneal pressures, lymph flow, and peritoneal space compliance. The model's predictions accurately mimic clinical observations in ascites, including the magnitude and time course of changes observed following paracentesis or diuretic therapy

COMPARATIVE ULTRASTRUCTURAL EFFECTS OF CLOFIBRATE ON HUMAN (HEP EBNA2) AND RAT (FAO) HEPATOMA CELL LINES

Clofibrate and other structurally related compounds such as ciprofibrate. fenofibrate, nafenopin, are hyperlipoproteinemias. They effectively reduce plasma triglyceride and cholestrol levels and in many instances increase the level of plasma high density lipoprotein. The purpose of the present study was to investigate and compare the ultrastructural effects of Clofibrate on human (Hep EBNA2) and rat (FaO) hepatome cell lines. Using electron microscopy and ultrastructural cytochemistry, we have shown that the mean number of peroxisomes per unit area of cell increased when the FaO cells were treated with 0.5 mM Clofibrate for 5 days. In addition, Clofibrate induced the occurrence of annulate lamellae. On the other hand, such ultrastructural changes were not observed in the Clofibrate treated Hep EBNA2 cells. The two hepatoma cells lines are appropriate for studying the effects induced by the action of the fibrate drugsLe clofibrate est un agent hypolipémiant utilisé en pharmacothérapie pour le traitement de l'hyperlipidémie et de l'hypercholestérolémie, sources majeures des troubles cardiovasculares. L'objet du présent travail a été d'analyser et de comparer les effets engendrés par ce composé chimique sur l'ultrastructure des hépatomes humains (Hep E B N A 2 ) et de rat (FaO). Les observations effectuées en microscopie électronique associant la cytochimie lútrastructurale ont permis de révéler que les traitements pendant 5 jours des hépatomes FaO par le clofibrate à la concentration de 0,5 mM dans le milieu de culture induit une prolifération des peroxysomes, organites cytoplasmiques dont les enzymes sont impliquées dans divers métabolismes oxydatifs. Cette augmentation du nombre des peroxysomes est accompagnée par l'apparition de lamelles annelées. De telles modifications ultrastructurales ne sont pas observées dans les hépatomes humains Hep E B N A 2 exposés au clofibrate. Les mécanismes responsables de cette différence dans la réponse des hépatomes murins et humains au clofibrate sont désormais analysé